The vegetative mushroom mycelium needs a selective medium in which to colonize. This medium is referred to as compost. Compost, which is a combination of different materials, makes the end product balanced with the guidelines set for carbon, nitrogen, moisture, Ph, ash and ammonia. There is no set formula for compost, since one can select materials from a wide variety. Once the materials and their amounts have been chosen, the dynamic process of composting occurs in a two phase aerobic thermophilic sequence, in which bacteria actinomycetes and fungi act in a sequence of dominance.
Phase I is the outdoor segment and involves a temperature range of about 140.degree. F.-170.degree. F. Its purpose is to promote healthy growth of thermophilic bacteria. Phase I results in (1) the formation of homogeneous material by mixing with the addition of water, until the mixture contains 72%.+-.2% water; (2) the initiation of microbiological fermentation of the compost through aerobic thermophilic micro-organisms which convert waste material to organic protein, carbohydrates and vitamins; and (3) the carrying out of caramelization.
Phase II is the indoor segment and has as its purpose the pasteurization and final conditioning of the compost by microbial conversions by means of aerobic thermophilic actinomycetes and fungi.
Pasteurization has been a major development in the commercial mushroom industry. The purposes of pasteurization are: (1) to destroy competitor moulds, pathogens and pests which can be achieved by a uniform temperature of 140.degree. F. for thirty minutes; and (2) to initiate the rapid growth of aerobic thermophilic actinomycetes, which thrive between 130.degree. F. and 150.degree. F. and are responsible for the selective nature of the compost.
Two types of efficient Phase II are low temperature and modified low temperature where there has been inefficient Phase I. For low temperature Phase II the following steps are used: (1) fill; (2) pre-pasteurization for aerobic thermophilic fungi growth at 115.degree. F. to 130.degree. F.; (3) pasteurization for aerobic thermophilic actinomycetes action growth at 130.degree. F. to 150.degree. F.; and (4) post-pasteurization for aerobic thermophilic fungi growth at 115.degree. F. to 130.degree. F. Modified low temperature Phase II uses the steps of: (1) fill; (2) pre-pasteurization for aerobic thermophilic bacteria at 130.degree. F. to 145.degree. F.; (3) pasteurization for aerobic thermophilic bacteria at 140.degree. F. to 150.degree. F.; and (4) post-pasteurization either for twenty-four hours for aerobic thermophilic actinomycetes at 135.degree. F. to 140.degree. F. or for aerobic thermophilic fungi at 115.degree. F. to 130.degree. F.
Inefficient Phase II can occur with the steps of: (1) fill; (2) pasteurization (with or without pre-pasteurization) with aerobic thermophilic actinomycetes at 135.degree. F. to 145.degree. F. or anaerobic thermophilic bacteria at 150.degree. F. to 162.degree. F.; and (3) post-pasteurization where there is an over-ride at high temperature for a prolonged time and aerobic thermophilic fungi at 120.degree. F. to 130.degree. F. or a bottom out and recycle with distortion of aerobic thermophilic microbial dominance.
Due to the conventional methods of pasteurization and its inefficiencies, however, the grower may be confronted with several problems. Presently, live steam at 100 to 125 psi which is equal to approximately 330.degree. F., is used to obtain and maintain pasteurization of the air and bed temperature of 140.degree. F. Live steam, however, has numerous disadvantages. For example, one disadvantage is the inability to obtain a uniform temperature, which makes it necessary to lengthen the pasteurization time from 1/2 hour to 6 hours to insure the heat penetration to the cold portions of the compost, i.e., sideboards and bottom beds and house. Further in order to raise the air temperature, it is necessary to restrict the fresh air (oxygen) going into the mushroom plant or Phase II room almost completely.
By the lengthening of pasteurization, to enable the cold portions of the bed which occupy approximately 10% of the volume of compost to achieve 140.degree. F., it is most probable that the cores, the warmest portions of the bed which occupy approximately 70% of the volume, would achieve a temperature between 150.degree. F. to 162.degree. F.
The following summarizes the complexity of the problems caused with live steam:
(1) with temperatures of 150.degree. F. and higher, thermophilic bacteria are initiated, thus interrupting the sequence of an efficient Phase II;
(2) also by obtaining temperatures of 150.degree. F. plus, the thermophilic actinomycetes, which should flourish during pasteurization, are being destroyed at a rapid rate. Also, the heat which is generated by the biology of the thermophilic bacteria is the cause of the high and uncontrollable over-ride temperatures during the post-pasteurization period;
(3) even if the bed temperature is held below 150.degree. F., since the mushroom plant or Phase II room has been restricted of fresh air (oxygen) to allow the rise in air temperature, the aerobic microbial activity is also restricted due to lack of oxygen. It may be restricted so severely that anaerobic microbes will be initiated. This oxygenpoor state of pasteurization during the conventional Phase II can be more destructive to the aerobic thermophilic fungi and actinomycetes than the high temperatures discussed above. Also, since the aerobic microbial activity was restricted during pasteurization, during post-pasteurization when fresh air is being introduced into and exhausted from the mushroom house or Phase II room for cooling, it rejuvenates the microbial activity that generates heat, as discussed above, to add to temperature over-rides.
At present, with the conventional Phase II, it is common belief to the growers that for an efficient Phase II, one should have the capacity of moving 1 cfm (cubic foot per minute) per square foot of growing area per 100 ton of compost. (For example, 60 foot double=8,000 square feet; 100 tons=approximately 160 cubic yards of compost; thus, 8,000 square feet filled with 160 cubic yards needs the capacity of 8,000 cfm of fresh air.)
Live steam additionally is inefficient for uniformity. Conventionally the flow of live steam, when dumped into the mushroom house or Phase II room is:
(1) under 100 to 125 psi and acts like a vacuum which pulls the air from that part to the opposite side, causing a draft;
(2) since the live steam is at approximately 330.degree. F., which is much hotter than the air temperature, the excessive heat rises; and (3) since the heat source is approximately 330.degree. F., which is approximately 240% more heat than necessary, the warmest portion of the compost rises in temperature at approximately the same rate as the cold portions.
Other unpredictable occurences can prolong the time of Phase II. For example, the biological activity in the compost cannot be completed in as short a time as possible due to lack of oxygen and/or temperature. The off-shoot of this is that the energy of the compost, which is formed from the biological conversions, could become exhausted, thus leaving too high an amount of unconverted ammonia in the compost. Additionally due to an inefficient Phase I, many anaerobic microbes are formed, resulting in an inefficient Phase II, and yield is retarded.
The unfortunate fate of a prolonged Phase II or anaerobic microbial activity, is the unnecessary loss of dry matter (weight) which is the master key to yield efficiency.